Recent studies suggest that lasers might be useful for the ablation of athero-sclerotic lesions, but the use of lasers for the endoscopic detection and quantitation of atherosclerosis has thus far received little attention. The proposed research is oriented towards the development of a fluorescence angioscopic technique capable of detecting and quantifying superficial and deep structural alterations of the arterial wall. Since the wall of atherosclerotic arteries may vary considerably in thickness due to the eccentricity of the arterial lumen, safe laser ablation in the region of arterial stenoses requires information about deep structure not provided by angioscopic visualization of the intima. The structural properties of isolated human artery segments with and without atherosclerosis will be determined by four independent morphometric techniques: 1) angioscopy, 2) casting of the lumen, 3) photography of the opened artery for the planimetry of intimal lesions, and 4) microscopic examination for the measurement of wall thickness, intimal thickness, and cross-sectional dimensions of atherosclerotic lesions. The intimal surface at arterial sites with defined structure will be irradiated with UV and visible lasers, and autofluorescence spectra will be recorded. Relative fluorescence intensities such as the ratio of fluorescence peaks will be related to the structural data. In addition, derived fluorescence parameters will be used to produce fluorescence maps of the arterial surface. Preliminiary experiments suggest that the fluorescence characteristics of arteries provides useful information about structural alterations of the arterial wall, and the proposed work should answer the question whether laser fluorescence imaging will be useful for the survey of arterial structure during angioplasty.